The present invention relate to combustion systems. More particularly, the invention relates to an apparatus for detecting fouling or corrosion in burner tips within a fired equipment system.
The term “fired equipment” or “heat delivery system” refers to devices that utilize fire or flames to deliver heat to a system. Typically, fired equipment utilizes a fuel delivery system for controlled delivery of fuel to a combustion chamber or to a burner tip. As used herein, the term “fuel” may be a gas, a liquid, a flammable mixture (such as coal particles in an oil suspension), or any flammable substance that is amenable to controlled delivery through a burner tip. Examples of fired equipment include incinerators, heat exchangers, reactors, boilers, and the like. One common failure mode for processes that use fired equipment is fouling or corrosion of the burner tips or nozzles, which deliver fuel to the combustion chamber. Such fouling or corrosion can impact fuel delivery, and can result in system failure and sometimes plant shut down.
In the process industry, unplanned plant downtime events caused by fired equipment failure can be very expensive, including lost production costs and the cost of shutdown/start up. In addition to such costs, the events that caused the plant downtime can also result in safety issues, environmental issues, and faulty products. Devices to provide diagnostic information and to generate alarms are used in process control industries to avoid such unplanned events when possible.
One diagnostic technique involves the use of process variables (PVs), which are monitored, and if determined limits are exceeded, an alarm condition is reported. Such an alarm is really just a detection of a symptom of the failure. The actual cause of the failure is left to be determined or inferred from other process information available to the control room, or available at the instrument generating the alarm. While sometimes the instrument itself may be at fault, such a situation is becoming less likely as instrumentation achieves higher and higher reliability. Usually, an alarm event is generated based on an aspect in the process itself going bad.
Conventionally, burner tip fouling or plugging was detected by noting a low fuel flow to the fired device, or by inference based on the inability to achieve the desired target process temperature. In some embodiments, a fired equipment unit has multiple burner tips, making upstream detection somewhat difficult. Specifically, as a single burner tip within a set of burner tips becomes plugged or corroded, an upstream sensor may not detect any change in fuel flow to the burner unit having multiple burner tips, because some burner tips of the burner unit may simply produce a slightly larger flame. Alternatively, if the fuel is corrosive, a corroded burner tip may simply burn more fuel but less efficiently. Identifying which burner tip is actually plugged or corroded may be difficult if not impossible without shutting down the system.
Another problem associated with such systems is that fouling and/or corrosion of a burner tip typically causes lower heat output. Compensation for such lower heat output may include increasing fuel flow to the system. The increased fuel flow may result in increased flame output from other, unplugged burners, thereby creating an uneven heating situation or hot spots within the system. Uneven heating may result in decreased efficiency, decreased product quality, and various other undesirable results. Moreover, if the burners are burn more fuel because another burner is plugged, they may produce a flame that is hotter than that for which the burner is rated, thereby exposing the burner to a temperature greater than it can withstand. Such hot spots eventually can lead to premature failure of the tubes or separator walls. Within the process itself, such hot spots may ruin the process.
There is an ongoing need in the art for a fouling and corrosion detection system for predicting when a burner tip or other flow obstruction elements are becoming fouled or corroded, so that the system can be serviced. Embodiments of the present invention provide solutions to these and other problems, and provide other advantages over the prior art.